// const add = (a:number,b:number):number =>{
//     return a + b
// }

// const sub = (a:number,b:number):number =>{
//     return a - b
// }


// const mul = (a:number, b:number):number => {
//     return a * b
// }

// const xxxx: 类型 = 值 

// const add: (a:number,b:number) => number = (a,b) => { return a + b }
// const sub: (a:number,b:number) => number = (a,b) => { return a - b }
// const mul: (a:number,b:number) => number = (a,b) => { return a * b }
// const xxx: (a:number,b:number) => number = (a,b) => { return a / b }

type Fn = (a:number,b:number) => number

const add: Fn = (a,b) => { return a + b }
const sub: Fn = (a,b) => { return a - b }
const mul: Fn = (a,b) => { return a * b }
const xxx: Fn = (a,b) => { return a / b }
